Soften the mushrooms in a cup of cool water. Blanch the tomatoes in a pan with boiling water; drain them, peel them and deseed them then, after removing the cooking water, sieve them.Peel the onion, rinse it and chop it finely, dice the smoked bacon; rinse the parsley, dry it and chop it finely. Heat some oil in a saucepan add the onion and fry until soft.Add the bacon and brown, stirring with a wooden spoon; then, once drained and sliced, add the mushrooms and flavour for a minute. At last add the tomatoes, season with salt and pepper and simmer for 15 more minutes, stirring from time to time.In the meanwhile cook the pasta in plenty of boiling water. Drain it al dente, pour it in a pan with the sauce, add 2 tbsp of cooking water and flavour for a minute; add butter and grated parmesan, remove the pasta from the heat and mixing, fold in the ingredients.Pour the pasta in a serving dish, sprinkle it with parsley and serve immediately.